«CSAAR (7: 2010: Amman) Sustainable Architecture and Urban Development \ Edited by Steffen Lehmann, Husam Al Waer, Jamal AI-Qawasmi. Amman: The Center ...»
Most, if not all, Vietnamese traditional houses have mediating spaces such as verandah, porch, balcony, or loggia. These play an important role as a buffer against direct sunshine and rain and connect the house with the surrounding nature. The air under these spaces circulates naturally, providing thermal comfort for occupants. Occupants spend a lot of time in these spaces during the day because they can enjoy cool breezes and daylight, and feel a sense of community. When staying in a verandah or a porch, the view to streetscape is more open than when sitting inside the house. Therefore, the mediating spaces are built with enough space as weil as shade for family activities.
Sustainable Architecture and Urban 295 Figure 5. Layout ofHoi An urban Figure 6. A solar courtyard of a townhouses with the use of courtyards townhouse in Hoi An ancient town, to provide a moderate microclimate. Central Vietnam.
Image edited from Institute of International Culture Showa Women's University (2003, pAO).
Archetypical shading elements of the Vietnamese house include deep eaves, solar canopies and vertical screens. In the tropical climate, they avoid direct sunlight and rain on walls and external openings of the house. Selecting appropriate shading devices for the house is based on the orientation of housing facades. In Vietnam, the sun is in the south, thus north facades are shady all year round. Therefore, only canopies or verandahs on south elevation are needed to provide shade and air circulation. However, surrounding overhangs are used to protect the house from both sunlight and rain. The south elevation is thus important and become the front of most houses. Thick brick or earth walls with Iimited openings are used on the eastern and western elevations to avoid heat gain. As a result, even without the assistance of mechanical systems, indoor air temperature is remarkably comfortable.
Openings and air vents are used to make rooms airy. In the climate of Vietnam, the wider the openings are, the more natural ventilation is provided for the house. Natural ventilation replaces polluted and hot indoor air with a fresh and cool breeze. In some areas, ceiling fans in the house are combined with the natural ventilation strategy to provide more comfort. To increase the ventilation effect, openings and air vents are built on thc external walls, on interna!
partitions, and on the front doors of the house with a fonn of top balusters (Fig.7 & 8).
296 Phuong Ly, Janis Birkeland &Nur Demirbilek Figure 8. Popular air vents used in Figure 7. Balusters on doors as air vents for providing ventilation. vemacular Vietnamese housing.
Last but not least, green spaces are integrated with the Vietnamese house in fruity, herbal, and decorative gardens. They provide landscape, shade, air filtering, food and a reduction of the ambient temperature. On the front of the house, tall slender-trunk palms and herbai shrubs are planted to allow prevailing cool breezes into the house while lush vegetation used at the rear. In Northem Vietnam, rear gardens protect the house against northem cold strong winds in the winter. Gardens also incorporate with solar ponds to regulate the microclimate.
Pergolas, trellises, and hanging t10wer pots contribute to the pleasant living environment.
With skills and experiences handed down over many generations, loeal craftsmen and masons have obtained praetieal knowledge of material use. They use timber logged from local woods for housing frames. Non-wood plants such as bamboo and rattan are used in eonstruction in various areas as they are eost efficient and locally available. Combined with bamboo frames, rural housing uses inexpensiveness and environmental friendly thateh from riee sterns or nipa palms for roofing and walling. Additionally, materials from clay and earth such as fired-clay bricks and tiles are used to build floors, walls, and roofs. Local availability of these materials and simple hand-manufacturing teehniques have meant these products have been refined over the centuries.
Timber is popular in most types of Vietnamese vemacular architecture. It is selected for their durability in moist conditions and termite resistance. Timbers from g6 mit (jackfruit-wood), kiJn kiJn (peck-wood), and g6 lim (iron-wood) are chosen in eonstruction aceording to the value of the house. Timber is used to Sustainable Architecture and Urban Development 297 make trusses, frames, columns, girders, and beams in both rural and urban traditional houses which have a life span of several centuries.
Low-cost vemacular houses use bamboo and rattan for roofing and framing because of their rapid growth and their ready availability (Fig.9). They are treated using traditional means before use to reinforce their resistance to termites and decay. A thatched roof and wall are combined with a bamboo frame to provide a cool interior atmosphere because these materials have a low-heat transmission and high insulation properties. Bamboo fibres can be woven to make walls, shading overhangs, and solar screens of the house.
The double roof and yin-yang roof are commonly used in Central Vietnam because they can efficiently avoid heat. To provide a cool microc1imate, the double roof is comprised of a top thatched roof and a tile layer over a bamboo woven base or timber battens. Air can move into the gap between these layers to ventilate the roof space (Nguyen and Nguyen, 1995). The yin-yang roof is another type of c1imatic roof, which can shade itself from eastern and western sunshine thanks to its wavy configuration.
3.4 Housing structure
The structure of the vernacular house is made of a timber skeleton and components such as girders and beams, melded together by ties, mortises and joints without modern technical nails and bolts. Traditionally, a main or an auxiliary timber housing block has an odd number of tiered divisions (such as three, five, or seven) with or without two additional wings. Houses with the odd tiered divisions can dedicate the middJe compartment to worshiping Buddha and the owners' ancestors. In a cross section, timber trusses, formed by an arrangement of girders and columns, support a pitched tiled or thatched roof.
Diverse types 01' timber trusses have been used in Vietnamese vernacular housin over time accordin to re ional conditions Fi.1 I).
Name of thc truss Dia ram Northern Vietnam Keo su6t gid chieng (Truss with continued multi-layer beams)
Figure 11. Some examples oftimber truss archetypes used in various regions of Vietnam (Thai, 2005).
Sustainable Arehiteeture and Urban 4 Applying Traditional Characteristics of Vietnamese Vernacular Housing into Contemporary Buildings Contemporary housing in Vietnam shows environmentally problematie issues wh ich reduee residents' and eeosystems' health and eonsume more energy and resourees. Urban and rural planning regulations have resulted in very dense development patterns to aeeommodate an inereasing population. These regulations do not encourage housing eonfigurations that ean take advantage of prevailing winds. Most modem Vietnam housing does not have enough voids for natural air nows, and road direetion and vegetation limit the ventilation or shading of buildings.
Vietnamese vernaeular arehiteeture is a souree of preeedents for modem arehiteetural design in tenns of its environmental hannony and resouree efficieney. Learning from the vernaeular does not mean simply eopying traditional forms, massing, details or materials. However, by analysing vernaeular designs, general lessons or prineiples ean be drawn and applied to future designs (Rapoport 2006). Legislative and voluntary options ean eneourage an integration of available resourees on site, apply passive design solutions, use loeal and environmental-friendly materials, and seleet appropriate strueture for the house. Climate responsive strategies applied to eontemporary arehitecture ean enhanee living eonditions and a sense of plaee and eommunity while protecting eeosystem and the broader life support system.
This research develops guidelines for c1imatic housing in Vietnam that allows for design creativity and variety. These guidelines consider site analysis and organisation, passive design, material use, and housing strueture that ean create the sustainable environment for Vietnam.
4.1 Site analysis and organisation
A thorough analysis of the site can better utilise on-site resourees and avoid compromising eeosystems and cultural values. Contemporary houses, if having a well-integrated site based on vernaeular design, ean provide comfort and well being to oeeupants with limited energy and resourees. The following strategies
should be eonsidered:
- Understand the site contexts and eonditions - including the eeosystems and surrounding habitats, cIimatie patterns. topography and cultural inf1uences.
- Protect and improve surrounding natural water systems which regulate the microclimate and to faeihtate rain water runoff.
- Prioritise south racing buildings which can eapture cool breezes in summer and solar heat in winter (for housing in Northern Vietnam with a eold winter).
Seleet local vegetation to protect the house from solar aeeess and to ehannel the air into the building. Shrubs and slender-trunk palms are traditionally planted at the front, and lush and fruit trees are seleeted at rear for wind controL Phuong Ly, Jani8 Birkeland &Nur Demirbilek
- Integrate the house with courtyard for air cireulation, espeeially in urban houses whieh are eonfined to a closed plot (Fig.12).
- Combine passive cooling strategies with housing structure and shape to provide human comfort in Vietnam climate while saving resources.
- Harvest and purtfy rainwater to provide sufficient water for household use;
Apply different effieient methods to eollect potable water such as solar still and transpiration teehniques.
4.2 Passive cooling design strategies Passive cooling strategies can provide natural ventilation and protect the house from heat and rain: the greatest impacts on tropical housing. New technologies for contemporary housing can reduce the impacts of sun and rain but use energy needlessly. Following strategies can be taken into aceount when designing
- Construct houses on high ground level or on stilts for capturing natural breezes for ventilation.
- Maximise openable windows and air vents to provide natural air movements through the house. Use top balusters or top hung widows on doors to encourage cool breezes while providing privacy.
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- Use double windows with outside louvers and inside glazing to provide flexible control in all weather conditions.
Ventilate roof spaces naturally by installing air vents on gables and eave ceilings; Consider double roofs with air space in between for thermo-siphoning.
- Arrange narrow single rooms on the layout for natural cross ventilation and heat avoidance. In Northem Vietnam, for example, building with a ratio between its length and depth of 3.7 can maximally reduce sun radiation on all its facades (Fig.I3).
- Guide cool breezes through the building by using window fins, buffer spaces and court yards.
- Use shading devices such as overhangs and eaves for reducing unwanted heat gain, especially on south facades to shade windows. Moreover, the overhangs also control rain access.
Apply thermal insulation to roof, using natural insulation materials or an air gap.
- Use Iightweight structures rather than thermal mass construction to avoid heat storage affecting the house.
- Apply treHises, green walls, and green roofs to reduce heat gain from the exterior envelope, especially in urban buildings with limited land for gardens.
Although hi-tech materials are now imported and used in contemporary Vietnamese housing, local materials are more aesthetically and cIimatically appropriate. The house will help to create a sense of place if it is built with materials from its own region. Therefore, the use of materials for housing needs
to consider the principles below:
Janis Birkeland &Nur Demirbilek